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The red click beetle on the bark of an oak tree.

Study species

Elater ferrugineus or commonly known as the red click beetle is Sweden's second largest click beetle (17-24 mm). This beetle is one of the species that are associated with wood mould of hollow deciduous trees. Its main habitat in Sweden is oaks but also can be found in other tree species such as beech and elm. The populations of this species are affected by the fragmentation of its habitat and therefore they are classified as vulnerable by the Swedish Red list.

Study site and sampling strategy

Map of the study area. Dots - traps with beetle, crosses - empty traps. Deciduous tree distributions were marked in grey.

A total of 99 traps were placed systematically in a grid of 40 km × 40 km area in the province of Östergötland , Sweden. Additional strategic sampling in two areas: a) 78 traps within the study area (40 km x 40 km) and b) 47 traps in the entire Östergötland were used as validation data sets. 

The beetles were collected using a non-destructive pheromone-based trapping method, allowing the specimen to be released alive and marked with unique numbers after every catch. Traps were emptied every third day. 

Left - funnel trap. Right - vial and PCR tube contained with sex pheromones.

Database on deciduous trees in Östergötland were used to calculate tree densities at various spatial scales and related with the occurrence of the beetles. Deciduous tree species that were included in this study are listed in the table below:

Tree group

Species No. of trees
Quercus Oak 9303
Noble 1 Beech, Elm, Hornbeam 1715
Noble 2 Ash, Chestnut, Maple, Lime 6940
Rosales Apple, Wild cherry, Pear, Rowan, Swedish whitebeam 2389
Malpiphiales          Aspen, Willow, Poplar 6142
Fagales Alder, Birch 1695

The scales where tree density best explained beetle occurence were then used in predicting the beetle’s potential distribution.

Responsible for this page: Agneta Johansson
Last updated: 05/21/12